1. Technical Field
The present invention provides a machine for automated extraction of nucleic acid, especially a machine for automatic extracting nucleic acid from large-volume samples and thereby the volume of the samples can be concentrated.
2. Prior Art
With the development of biotechnology and the decoding of hereditary substances, more and more biology-related, or even forensic, labs and hospitals extract nucleic acid from specimens on a regular basis in order to conduct experiments or tests. Nucleic acid can be extracted and purified in many ways, the most common of which can be divided into the following three categories: column extraction, magnetic bead extraction, and reagent extraction, wherein reagent extraction can be further divided into organic solvent extraction and non-organic solvent extraction. While each extraction method has its pros and cons, column extraction is currently the safest and easiest in terms of operation and also the most effective.
The process flow of column extraction is briefly stated as follows. To start with, the treated specimen (e.g., treated with an anionic detergent in order to break cells, release nucleic acid therefrom, and denature protein) in a microcentrifuge tube is transferred to a purification tube, in which a purification membrane is provided and whose bottom end has a passageway through which a liquid can flow out of the tube. Generally, the specimen in the microcentrifuge tube is drawn out with a micropipette and injected into the purification tube from above. After that, the purification tube is inserted into a waste liquid tube, and the double-tube assembly is subjected to centrifugation in a centrifuge in order for the nucleic acid, which is negatively charged, to bind with and be adsorbed onto the purification membrane, which is positively charged. In the meantime, impurities are driven through the purification membrane by the centrifugal force and flow into the waste liquid tube through the passageway at the bottom end of the purification tube. The foregoing step is referred to as the “binding step”. Next, the “cleaning step” is performed by adding a cleaning liquid into the purification tube and starting centrifugation again to remove any impurities on the purification membrane and thereby increase the purity of the nucleic acid to be obtained. Lastly, the purification tube together with the nucleic acid-loaded purification membrane is transferred into a collection tube, in which an eluent of a specific salinity and pH value is subsequently added to change the electrical properties of the purification membrane, and the nucleic acid is separated from the purification membrane by centrifuging once more, then flows out of the purification tube, and eventually gathers in the collection tube. The last step is known as the “collection step”.
The column extraction method described above is rather complicated. While the market has been supplied with automated centrifugal column extraction machines, those machines are disadvantaged by a time-consuming extraction process and are unsuitable for extracting nucleic acid from large-volume samples because they must be equipped with a centrifuge and are subject to limitations imposed by the volume of the column